SkyChart III Release 3.5.1 Update

SkyChart III release 3.5.1, released on 7 May 2002, is an update to SkyChart III releases 3.0 through 3.5. It adds some major new features, and fixes a number of bugs that were present in previous versions. For a complete list of bug-fixes and feature improvements provided by this update, see the Release Notes section below. Both Macintosh and Windows users should download and install this update.

Release 3.5.1 of SkyChart III is only available as a downloadable update to previous CD-ROM releases. It is not available on a separate CD-ROM.

Also note that with release 3.5.1, the system requirements for SkyChart III have been changed. The Windows version of SkyChart III now has the following minimum system requirements:

There are now two Macintosh versions of SkyChart III: one for "Classic" Mac OS 8.6 - 9.2, and a "Carbon" version for Mac OS X. The Macintosh versions of SkyChart III have the following minimum system requirements:

Installation Instructions

To install this update, you must already have SkyChart III release 3.0 - 3.5 installed on your hard drive.

Click on one of the following links to download the appropriate version of the SkyChart III release 3.5.1 updater application to your computer:

Operating System Download Size Description
Windows 95/98/Me/NT/2000/XP SkyChart III Update 3.5.1 for Windows 4.4 MB (4,654,292 bytes) 32-bit Windows executable
Mac OS 8.6 - 9.2 SkyChart III Update 3.5.1 for Mac OS 8.6 - 9.2 5.6 MB (5,956,864 bytes) MacBinary-encoded Classic Mac OS application
Mac OS X SkyChart III Update 3.5.1 for Mac OS X 6.5 MB (6,902,528 bytes) MacBinary-encoded Carbon Mac OS application

The Macintosh versions are MacBinary-encoded; Macintosh users may need to obtain a uility like StuffIt Expander from Aladdin Systems in order to decode them.

After downloading the appropriate installer, double-click its icon to begin updating your current installation to release 3.5. Everything after that should be self-explanatory. If you have any questions, comments, or problems with the installation, please don't hesitate to send e-mail to, or call us toll-free during West Coast business hours at (866) 887-7827. If you find any bugs that are not addressed in this release, please tell us!

Problems with the Download?

If you have problems downloading these files, please check to make sure that the exact size of the file you've downloaded (in bytes) matches the file sizes specified above. If they do not match, the download was incomplete or corrupted. Send e-mail to, let us know which version you need, and we'll try to send it back to you by email.

Release Notes

release 3.5.1 (7 May 2002)

  1. The on-line documentation has been updated to HTML format. The Windows version uses the Microsoft HTML help engine; the Mac OS versions use the Apple Help system.

  2. Saturn's rings are now drawn correctly in red-screen mode, when color is turned off, or when the chart mirror-imaging is turned on or off.

  3. Rendered planet images are now drawn correctly when mirror imaging is turned on

  4. Telescope control and serial port I/O is now working in the Mac OS X version of SkyChart III.

  5. The Mac OS X version of SkyChart III is now a native Mach-O executable; it will only run under Mac OS X (not Mac OS 8.6 - 9.x with CarbonLib installed).

  6. A fatal crash that occurred in the Mac OS X version when red screen mode was turned on has been fixed.

  7. The Windows version now enumerates and lists the serial ports correctly, instead of listing all possible COM and LPT ports in the Telescope Connection... dialog box.

  8. If a telescope is connected while opening a settings file, the connection is closed when the file opens. This prevents the program from erroneously writing data to the serial ports.

  9. The right/and or bottom margins of the chart should no longer be cut off on printouts.

release 3.5 (13 August 2001)

  1. There are now two Macintosh versions of SkyChart III: a "Classic" version for Mac OS 8.6 - 9.1, and a "Carbon" version for Mac OS X. The Classic version is designed to run on any PowerPC Macintosh computer with Mac OS 8.6 or higher. It will also run under Mac OS X, but only within a "Classic" environment— in other words, it will not run as a native Mac OS X application.

    The Carbon version is specifically designed for Mac OS X. It will run as a "native" Mac OS X application, and take take advantage of new Mac OS X features such as protected memory, pre-emptive multitasking, and the "Aqua" user interface. It will also run under Mac OS 8.6 and higher if the "CarbonLib" extension, version 1.1 or higher, is present. (CarbonLib 1.1 comes with Mac OS 9.1, and can be installed on Mac OS 8.6 or higher.)

  2. SkyChart III can now render star images and planet surfaces in 32-bit color. The models used to render the planets are mostly derived from NASA spacecraft imagery, and as a result, the planetary images generated by SkyChart III are among the most realistic of any sky simulation program.

    This new feature can be turned on and off by selecting the new Rendered Objects item in the Draw menu. Please note that this feature is very CPU intensive, and requires at least a PowerPC G3- or Pentium II-class processor to run well. Currently, all of the rendering is done in software; future versions may take advantage of 3D graphics hardware to accelerate object rendering. Also, for the best results, your monitor should be set to 16- or 32-bit color; rendered images will look very poor in 8-bit (i.e. 256 color) mode.

    Here are some examples of scenes drawn the old way (bottom row), and rendered the new way (top row). You can click on any of the small "thumbnail" images below to display a full-sized version.

    Jupiter from Io Total solar eclipse Saturn
  3. SkyChart III can now save charts generated by the program in a variety of new graphic file formats: GIF, TIFF, and JPEG. The GIF and JPEG file formats, in particular, allow the easy publishing of charts generated by SkyChart III to the World Wide Web. In addition, the Macintosh versions can save charts in PICT format, and the Windows version can save charts in BMP and WMF format (this is as before.)

  4. SkyChart III can now export animations as well as charts. Animations can currently be exported as animated GIF files, viewable in any web browser. Future releases may also add the ability to save animations as QuickTime and/or MPEG video files.

    The following image is an animated GIF file generated by SkyChart III showing the movement of the stars in the Big Dipper over a period of 300,000 years, starting from the year 150,000 B.C. Each frame of the animation represents 1000 years. The total size of the animated GIF file is 2.2 MB, so it may take a while to load. The animation will loop when completed.

    Big Dipper 150,000 B.C. to 150,000 A.D.

  5. Jupiter's central longitude is now computed using System II, based on the rotation rate of Jupiter's atmosphere at high latitudes. Previously, Jovian central longitudes were computed using System III, based on the rotation rate of Jupiter's internal magnetic field. As a result of this change, SkyChart III now displays Jupiter's Great Red Spot in (roughly) the correct position. Because the Great Red Spot drifts unpredictably by 10-20 degrees in longitude over periods of months to years, SkyChart III can't provide its position accurately enough for, e.g., meridian crossing times to 1-minute precision. But the current version ought to be accurate enough to tell whether or not the GRS will at least be visible at a given time. Please note: if you are intending to use SkyChart III for this purpose, make sure the light time correction is turned on! (See below).

  6. The central longitudes of Uranus and Neptune are now computed using the official IAU 1991 values for their rotation rates, taken from the 1993 Explanatory Supplement to the Astronomical Almanac. These values are based on observations from the Voyager II mission. They are much more accurate than the 1985 IAU values used in previous versions of SkyChart III, which are derived from ground-based observations. However, the central longitudes for Uranus and Neptune listed in the Astronomical Almanac are apparently still computed using the old, 1985 rotation rate values. Therefore, while SkyChart III's results for these planets may differ from the Almanac's, they are probably more realistic.

    Finally, the rotation of Pluto's moon Charon is now computed correctly (in previous versions of SkyChart III, Charon did not not rotate at all!)

  7. SkyChart III now corrects planetary central longitudes for light time only when the Light Time option in the Precision dialog box (under the Computation menu) is turned on. Previously, this correction was always applied, regardless of this setting, which was confusing because there was no indication that anything changed when the option was turned off or on. If you need SkyChart III to accurately display planet surface features, make sure this feature is turned on. If not, SkyChart III will compute planetary central longitudes at the chart display time (incorrect) instead of at the time light left the planet (correct). For example, light time from Jupiter can be more than 45 minutes, while Jupiter rotates in less than 10 hours. In those 45 minutes, Jupiter rotates almost 30 degrees— enough that the visible part of the planet's surface will be substantially different that if those 45 minutes had not been taken into account.

  8. Several settings were not being properly stored in SkyChart III's settings files. These were the solar-system object "Limiting Magnitude", the "Rendered Objects" setting, and the "Show Mouse Coordinates" setting. This bug has been fixed. The settings file format has been updated slightly to accommodate these new values, but is still compatible with previous versions of the program.

    This release of SkyChart III also includes some new and updated settings files to show off the new graphics capabilities. These are placed in the "Demo Settings Files" folder; as in previous versions, you can open these with the Open Settings command, in the File menu.

  9. A bug that prevented the program from launching on some Mac OS computers has been fixed.

  10. A bug which sometimes prevented the Windows version of the program from printing properly has been fixed. Also, the Windows printing progress dialog has been modernized.

  11. When saving files, the Windows version of SkyChart III now appends the proper file-type extension (e.g. ".jpg" for JPEG image files, ".sks" for SkyChart Settings files, etc.) to the file name, if it was not already entered by the user in the "Save File" dialog.

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This page was last updated on 7 September 2002.